Objectives Ankylosing spondylitis (AS) is associated with increased risk of cardiovascular problems, including complications such as conduction defects and arrhythmias, which might lead to increased morbidity and/or mortality. The objective of the present study is to evaluate the electrocardiographic (ECG) parameters, including T-peak to T-end intervals (Tpe), Tpe/corrected QT (QTc) ratio, heart rate variability (HRV), and heart rate turbulence (HRT) in AS patients. Methods Seventy-six AS patients and 55 control subjects were included in the study. 12-lead ECG and 24-h Holter monitoring recordings were obtained. Tpe and Tpe/QTc were measured using the 12-lead ECG and HRV and HRT parameters were assessed using 24-h Holter ECG recordings. Subjects were assigned into three groups based on their HRT parameters (Tonset (TO) and Tslope (TS)) (HRT-0, normal TO or TS; HRT-1, abnormal TO or TS; HRT-2, abnormal TO and TS). Results Tpe was prolonged and Tpe/QTc ratio was higher in AS patients (p < 0.001 for both). Moreover, Tpe and Tpe/QTc ratio significantly correlated with disease duration. All HRV parameters (VLF, LF, HF, SDNN, SDANN, ASDNN, rMSSD, pNN50) were decreased in AS patients in comparison with those in control subjects (p < 0.05 for all parameters). Controls were significantly more likely to have normal TO and TS (82% vs 53%, p < 0.001). There was negative correlation between Holter parameters and disease duration, as well as Tpe and Tpe/QTc ratio (p < 0.05 for all parameters). Conclusions This study demonstrated that AS patients have disrupted ventricular repolarization (increased Tpe, Tpe/QTc ratio). Results suggest a decreased cardiac impact of the parasympathetic system in AS patients.